You could ask him what changed, I think the answer to that would be a good way to see whether its genuine or not. Alternatively you could just leave it and see how things go from here which is probably what I would do (but I have major avoidance issues so you should have a good think about what you want). Sometimes its good to make things easier for yourself, just enjoy getting called the right name and pronouns even if it does turn out to be temporary, especially when you're so young and not out of the family home yet. If you're leaving things alone for now I would be careful about letting your guard down though, especially when he's been reading terf literature. Maybe he managed to somehow buy the book without spotting the transphobia plastered over the front cover but I'd be prepared for worst case scenario. This all could be genuine but it could also be some kind of reverse psychology experiment, personally though I 'd just enjoy the calm and getting called the right things and wait to see what he does.